As cellular communication has become prevalent, it is not uncommon for a person to carry a cellular telephone device with them on a daily basis. Because of this, there is desire by local police and fire departments to use a corresponding cellular telephone device to help locate a missing person, for example, a person trapped in a collapsed building or a fugitive. Conventional approaches to cellular telephone device location include systems comprising a plurality of sensors. These systems typically use a triangulation method to determine the location of the cellular telephone device.
One approach to cellular telephone device location is disclosed by U.S. Pat. No. 6,407,703 to Minter et al. The system of Minter et al. includes a plurality of sensors situated in multiple locations/platforms. The system uses angle of arrival (AOA), time difference of arrival (TDOA), and terrain altitude information from signal intercepts from the cellular telephone device to determine the location thereof. The sensors use accurate time synchronization for determining the TDOA of the intercepted signals
Another approach to locating a cellular telephone device is disclosed in U.S. Pat. No. 7,187,327 to Coluzzi et al. This system also includes a plurality of sensors using TDOA and time of arrival measurements of signals received from the cellular telephone device to determine the location thereof. The sensors in this system are also synchronized.
Another approach to locating a cellular telephone device is disclosed in U.S. Pat. No. 7,203,500 to Leeper et al. This system uses a wireless transceiver device to determine range to a companion wireless transceiver device, for example, the cellular telephone device, with signal propagation time measurements. Another approach to locating a cellular telephone device is disclosed in U.S. Pat. No. 7,057,556 to Hall et al. This system includes a plurality of sensors also using TDOA to determine the location of the cellular telephone device.
Another approach is disclosed in U.S. Pat. No. 5,719,584 to Otto, assigned to the present application's assignee, Harris Corporation of Melbourne, Fla. This system uses a plurality of ground based sensors to determine a location of the cellular telephone device by measuring TDOA and AOA values. This network of sensors is also synchronized.
An approach to locating a cellular telephone device within a high-rise structure is disclosed in U.S. Pat. No. 7,203,497 to Belcea. This system includes a plurality of sensors deployed throughout the structure that use signal propagation time measurements to determine the approximate location of the cellular telephone device within the structure.
The prior art systems for location of cellular telephone devices may suffer from several drawbacks. For example, these systems use multiple sensors that are synchronized for generation of TDOA measurements. The systems are also complex and expensive, and require multiple sensors on different platforms. The systems also provide inaccurate location data if the sensors are not properly deployed.